Linnaeus published 22 names under Chrysanthemum L. (Linnaeus, 1753,
1759,
1763,
1767b). According to Jarvis (2007) 18 out of the 22 Linnaean names are already typified. Among the remaining 4 untypified names, two (Chrysanthemum italicum L., and C. achilleae L.) are applied to taxa belonging to the Tanacetum corymbosum group (see e.g. Heywood, 1976a; Greuter, 2006–2009). Other taxa linked to this group (Pyrethrum cinereum Griseb., P. clusii Fisch. ex Rchb., P. daucifolium Pers., P. tenuifolium Ten.) need a nomenclatural revision which is here presented as part of the studies on Linnaean names and the cooperation in the treatment of the Asteraceae for the new edition of the Flora of Italy (see e.g. Del Guacchio & Iamonico 2015; Iamonico, 2013,
2015; Iamonico & Hjertson, 2015; Iamonico & Managlia, 2014; Iamonico & Peruzzi, 2016; Iamonico et al., 2014).

MATERIALS AND METHODS

The nomenclatural and taxonomical study, which is here presented, was carried out by an extensive analysis of literature (protologues included), personal field investigations, and the examination of the specimens (see Appendix 1) kept in the Herbaria B, G, GOET, GZU, JE, K, L, LINN, P, PH, RO, W and WU (acronyms according to Thiers, 2018–).

The articles cited through the text follow the Shenzen Code (Turland et al. 2018) which is further referred to as ICN (International Code of Nomenclature for algae, fungi, and plants).

BACKGROUND

Chrysanthemum achilleae L.

Chrysanthemum achilleae was published by Linnaeus (1767b: 562) through a short diagnosis and a description. A Micheli’s illustration (Micheli, 1729: Tab. 29) was cited and it is original material for the name. No specimens useful for the typification purposes were traced (see also Jarvis, 2007), so this illustration is designated in this work as the lectotype of the name Chrysanthemum achilleae. I here recognize this taxon at subspecies rank of Tanacetum corymbosum, as already proposed by Greuter (in Greuter et al., 2003: 43) (see also the discussion of C. achilleae/C. italicum in the section “Nomenclatural and taxonomic remarks”).

Chrysanthemum italicum L.

Linnaeus’ protologue of Chrysanthemum italicum (Linnaeus 1767a: 116[1]) consists of a short diagnosis (“CHRYSANTHEMUM foliis bipinnatis serratis, florum radiis disci longitudine, caule procumbente”), and one synonym cited from Micheli (1729: 34) who provided an illustration[2] (“Tab. 29”) which is part of original material; the collector (“Arduini”), and the provenance (“Habitat in Italia”) were also provided; Linnaeus also highlighted a morphological similarity with C. millefoliatum (Linnaeus, 1767b: 563, nom. superfl.[3], Arts. 52.1. and 52.2 of the ICN). There is one sheet at LINN (no. 1012.21) bearing parts of a probably same plant whose features match the diagnosis, and the Linnaean annotation “chrysanth[emum] italicum Ard[uino]”. The plant was sent from P. Arduino to C. Linnaeus, and it can be considered an ante-1767 addition to the collection and original material for the name (Jarvis, 2007). I have not been able to locate any further original material in any other Linnaean or Linnaean-linked herbaria (see also Jarvis, 2007). Among the elements selected (specimen from LINN, and illustration by Micheli) I here designate the first one as the lectotype of the name Chrysanthemum italicum over the illustration because of its potential ability to provide a larger number of additional characters (micro-morphological, chemical, molecular, etc.) that cannot be examined by images (Jarvis, 2007: 21–22).

Chrysanthemum italicum is considered as a heterotypic synonym of C. achilleae, as is discussed in the section “Nomenclatural and taxonomic remarks”.

Chrysanthemum tanacetifolium Pourr.

Pourret (1788: 311) published Chrysanthemum tanacetifolium thorugh a short diagnosis (“foliis bipinnatis, pinnis inciso-serratis, caule ramoso pedunculis axillaribus longis multifloris”) and provided some localities (“Aux environs de Narbonne, à Cascastel, l’Espinassiere, & c.”). I have not been able to trace specimens which are part of the original material. As a consequence, on the basis of the Art. 9.8 of the ICN, a neotypification is required. Unfortunately, no specimen collected by Pourret was found. I select a specimen (P 00731963) collected at Montpellier, which displays morphological characteristics matching the Pourret’s diagnosis. The P00731963 is designated in this work as the neotype of the name Chrysanthemum tanacetifolium. Based on the morphology of this specimen (especially concerning the leaf segments (2nd order) which are ovate-lanceolate), and according to the current concept in Tanacetum (see e.g. Heywood, 1976a: 170–171), the name C. tanacetifolium is to be considered as heterotypic synonym of Tanacetum corymbosum subsp. corymbosum.

Pyrethrum cinereum Griseb.

Grisebach (1844: 203) provided a detailed diagnosis, the provenance (“In Macedonia et Bithynia[…] Pr. Palanka distr. Kostendil […] (Friedr.) [= E. Friedrichsthal]pr. Bolu (Pest.) [= F. Pestalozza]”), and the habitat (“in pascuis lapidosis […] alt. 2000ʹ–3000ʹ”) in the protologue of Pyrethrum cinereum. There are two specimens at GOET (where the most of the Grisebach specimens are preserved—see Stafleu and Cowan, 1976: 1007), GOET 002103 and GOET 002109 bearing plants collected respectively by E. Friedrichsthal at Palanka (Macedonia), and F. Pestalozza at Bolu (Turkey). A third specimen is kept at W (W 0051161) and bears a plant collected by E. Friedrichsthal at Palanka. According to the Art. 9.6 of the ICN, these three specimens (two at GOET, and one at W) are syntypes. Some considerations are to be made on these three specimens:

1. both E. Friedrichsthal and F. Pestalozza were explicity reported by Grisebach (1844) in the title page of his Spicilegium as collaborators of the work;

2. the localities indicated in the labels perfectly match the protologue;

All thing stated, I here consider these three specimens as part of the original material, and designate that at GOET 002103 (it appears to be better preserved) as the lectotype of the name Pyrethrum cinereum. I here recognize this taxon at subspecies rank of Tanacetum corymbosum, as already proposed by Davis (1975: 262).

Pyrethrum clusii Fisch. ex Rchb.

Reichenbach (1831: 231–232) named this species in honour of C. A. Clusius who described in his Rariorum Plantarum Historia (Clusius, 1601: 338) a “Tanacetum inodorum I”. This polynomial was reported by Reichenbach (1831: 232) as synonym of P. clusii. The illustration provided by Clusius (1601) is part of the original material and is designated in this work as the lectotype of the name Pyrethrum clusii.

According to the current concept in Tanacetum (see e.g. Heywood, 1976a: 170–171), and on the basis of the lectotype of P. clusii, this name seems to be referred to Tanacetum corymbosum subsp. subcorymbosum. However, since the typification of Chrysanthemum subcorymbosum Schur (basionym of T. corymbosum subsp. subcorymbosum) was not possible to achieve (see Note 6 in “Taxonomic treatment”), I here considered P. clusii as doubt synonym of T. corymbosum subsp. subcorymbosum. In anycase, although P. clusii would have nomenclatural priority (1831 vs. 1859), the combination at subspecies rank (here accepted as better taxonomic rank) was published earlier for C. subcorymbosum (1936 vs. 1976—see the section “Taxonomic treatment”). As a consequence the name to be used at subspecies rank would be however T. corymbosum subsp. subcorymbosum (Schur) Szafer & Pawłowski.

The Reichenbach’s name is to be considered as a later homonym of Pyrethrum clusii Tausch (see the discussion below), and so illegitimate according to Art. 53.1 of the ICN. Dostál (1950: 1603) and Heywood (1976b: 272) proposed new combinations of the Reichenbach’s name at subspecies rank under Chrysanthemum and Tanacetum, respectively. On the basis of the Art. 58.1 (and see the Ex. 2) “The final epithet in an illegitimate name may be re-used in a different name, at either the same or a different rank; or an illegitimate generic name may be re-used as the epithet in the name of a subdivision of a genus. The resulting name is then treated either as a replacement name with the same type as the illegitimate name”. As a consequence, the Dostál’s and Heywood’s combinations are legitimate and to be considered as replaced names of Pyrenthrum clusii.

Tenore (1815: 50) described Pyrethrum teniufolium through just a diagnosis (any locality or habitat were cited). The same author published a more complete treatment of the species in the 2nd volume of Flora Napolitana (Tenore, 1820: 236) where he provided a detailed description, some localities (“…monti di Abruzzo, alla Majella, al Gran sasso…”), an illustration (“Tav. LXXX”, image available at http://www.ortobotaniconapoli.it/paginadimenu.htm), and a comparison with the similar P. corymbosum. I traced three specimens at K (K 000928497, image available at http://apps.kew.org/herbcat/getImage.do?imageBarcode=K000928497) and G (G 00450830, and G 00450834, images available at http://www.ville-ge.ch/musinfo/bd/cjb/chg/adetail.php?id=317570&base=img&lang=en). The K 000928497 specimen bears a plant collected by M. Tenore in May 1830 in the locality “Majella M.te de Fiori”, and (date of collection post-1815) cannot be considered as part of the original material. The G00450830 specimen was collected “In Majella”, but the collection date is lacking and I cannot be sure it was an atne-1815 addition to the collection, so I avoid this specimen for he lectotypification purpose. On the contrary, the G 00450834 specimen was collected in 1814, as indicated in the original label. Moreover it was reported “nob.” [nobis]. The morphological characteristics of the plant beared in the G 00450834 specimen matches both the diagnosis by Tenore (1815: L), and the later description by Tenore (1820: 236). I designate in this work the specimen G 00450834 as the lectotype of the name Pyrenthrum tenuifolium. The morphology of the lectotype [leaf blades 2-pinnatipartite with segments (2nd order) ovate-lanceolate] allows to synonymized the Tenore’s name with Tanacetum corymbosum subsp. achilleae.

The Tenore’s name is to be considered as a later homonym of Pyrethrum tenuifolium Willd., and so illegitimate according to the Art. 53.1 of the ICN.

Chrysanthemum corymbosum is currently recognized under the genus Tanacetum L., as T. corymbosum (L.) Sch. Bip., a variable species including four subspecies (see e.g. Greuter, 2006–2009): subsp. corymbosum, subsp. achilleae, subsp. cinereum (Griseb.) Grierson, and subsp. subcorymbosum (Schur) Pawl. The type of C. corymbosum s. str. (≡ C. corymbiferum) [lectotype (LINN, Herb. Linn. No. 1012.13) designated by Humphries in Jarvis & Turland (1998: 358); image available at http://linnean-online.org/10439/)] shows a plant with leaves pinnatipartite, the segments having margins toothed or incised. On the whole, the morphological configuration of C. corymbosum subsp. corymbosum [both considering the lectotype, and the current concept of the species (see e.g. Heywood 1976a: 170–171)] does not match those of C. achilleae which type show leaves clearly 2-pinnatipartite. C. achilleae cannot be associated neither with the subsp. cinereum, nor with the subsp. subcorymbosum that are characterized in having pinnatipartite leaves. The Micheli’s illustration (lectotype of C. achilleae) shows the segments of 1st order about two times longer than wide and those of the 2nd order ovate with margins mainly toothed, while the specimen Herb. Linn No. 1012.21 at LINN (lectotype of C. italicum; image available at: http://linnean-online.org/10447/) is a plant with segments (1st order) 2.5–3.0 times longer than wide, and segments (2nd order) lanceolate incised to laciniate. On the basis of the lectotypes of C. achilleae, and C. italicum, these two names appear to be referred to different taxa. However, the forms with leaves 2-pinnatipartite have segments (2st order) which margins configuration vary continuously from toothed to deeply incised (pers. observ.). The type of C. achilleae and C. italicum seems to represent the limits of the range concerning the character of the margin of the leaves segments (2st order). I here propose to treat the names Chrysanthemum italicum and C. achilleae as heterotypic synonyms. Since both names were published in the same date (15–31 october 1767 according to Stafleu & Cowan (1981: 107), the Art. 11.4 of the ICN cannot be applied, and I am obliged to consider Art. 11.5 instead. Arcangeli (1882: 353) was the first author who united both names, choosing Chrysanthemum achilleae (sub Pyrethrum achilleae) which deserves priority.

As a whole, and on the basis of the personal examination of specimens collected in Europe and Middle Asia, I highlighted two main morphological groups in Tanacetum corymbosum, i.e. corymbosum/subcorymbosum/cinereum (group I) and achilleae/daucifolium (group II). The group I is characterized in having the leaf blades 1-pinnatipartite with the segments toothed or incised, while the group II shows blades 2-pinnatipartite with segments (2nd order) toothed to incised or linear. Differential characters among the taxa included in each group refer to bracts of capitula and hairness of leaves (group I), and shape of leaf segments of 2nd order (group II) as reported in the following diagnostic key:

2. Involucral bracts of capitula with a broad blackish-brown margin (each margin up to 1/3 wider of the total size of the bract)
........................................................................................................T. corymbosum subsp. subcorymbosum

Thanks are due to the Director and Curators of all the herbaria cited.

NOTES01

Linnaeus also published the name Chrysanthemum italicum in Systema naturae (Linnaeus, 1767b: 563), where he quoted the reference to his Mantissa (“Mant. 116”).

02

The Micheli’s reference was also cited in the synonymy of Chrysanthemum achilleae (see discussion under this name)

03

Linnaeus (1767b: 563) published the name Chrysanthemum millefoliatum citing as synonym Anthemis millefolia L. (from Linnaeus, 1753: 896). Since A. millefolia [now Tanacetum millefolium (L.) Tzvelev, lectotype at LINN (No. 1012.22) designated by Humphries in Jarvis & Turland (1998: 352), image of the lectotype available at: http://linnean-online.org/10448/] was validly published, C. millefoliatum is a superfluous and illegitimate name according to the Arts. 52.1 and 52.2 of the ICN.

04

The Podlech’s name is an isonym of the previous proposed combination Tanacetum corymbosum var. tenuifolium (Willd.) Briq. & Cavill. (see the paragraph “Taxonomic Treatment and typification of the names”).

05

The name Chrysanthemum corymbiferum is clearly an orthographic variant of C. corymbosum L. (1753: 890), as noted by Stearn (1974: 632). Linnaeus (1763: 1251) in the 2nd Edition of Species Plantarum again used the epithet “corymbiferum”, but in conjunction with the same diagnosis and synonyms associated with C. corymbosum in the 1st Edition of Species Plantarum (Linnaeus, 1753: 890). In the 12th Edition of Systema Naturae (Linnaeus, 1767b: 562), Linnaeus again used the same diagnosis, but reverted to the use of “corymbosum”.

06

As original material was not found, a neotypification would be required (Art. 9.7). However, despite repeated requestes, I have not received replies from Curators of some Herbaria in which the Schur’s collection is preserved. So, I cannot be sure that a lectotype is not in extant and, in the case that original material will be found, any neotypification will be superseded. As a consequence I prefer to avoid the proposal for a neotype for the time being. For this reason Pyrethrum clusii was reported a doubtful synonym of Chrysanthemum subcorymbosum.